"which forms of light are lower in energy and frequency than the light that our eyes can see"

Electromagnetic radiation covers a wide spectrum of which we can only see an extremely small sliver (wavelength between 390 nm and 740 nm).

The electromagnetic radiation with a wavelength greater than 740 nm meets the given criterion. This mainly consists of infrared, microwave, and radio waves. 

If you want to see something really interesting, Google the wavelength of Hawking radiation! 

If you're looking for an even spread of clay, silt and sand, add a considerable amount of sand and some clay until the 3 even out". soil texture triangle. silty clay loam soil is approximately 20 percent or less sand, 25 to 40 percent clay, and 40 to 70 percent silt.